Sunday, September 19, 2010

Potatoes and Human Health, Part I

Potatoes: an Introduction

Over 10,000 years ago, on the shores of lake Titicaca in what is now Peru, a culture began to cultivate a species of wild potato, Solanum tuberosum. They gradually transformed it into a plant that efficiently produces roundish starchy tubers, in a variety of strains that suited the climactic and gastronomic needs of various populations. These early farmers could not have understood at the time that the plant they were selecting would become the most productive crop in the world*, and eventually feed billions of people around the globe.

Wild potatoes, which were likely consumed by hunter-gatherers before domestication, are higher in toxic glycoalkaloids. These are defensive compounds that protect against insects, infections and... hungry animals. Early farmers selected varieties that are low in bitter glycoalkaloids, which are the ancestors of most modern potatoes, however they didn't abandon the high-glycoalkaloid varieties. These were hardier and more tolerant of high altitudes, cold temperatures and pests. Cultures living high in the Andes developed a method to take advantage of these hardy but toxic potatoes, as well as their own harsh climate: they invented chuños. These are made by leaving potatoes out in the open, where they are frozen at night, stomped underfoot and dried in the sun for many days**. What results is a dried potato with a low glycoalkaloid content that can be stored for a year or more.

Nutritional Qualities

From a nutritional standpoint, potatoes have a bad reputation, but this is undeserved in my opinion. If I had to pick a single food to eat exclusively for an extended period of time, potatoes would be high on the list. One reason is that they contain an adequate amount of complete protein, meaning they don't have to be mixed with another protein source as with grains and legumes. Another reason is that a number of cultures throughout history have successfully relied on the potato as their principal source of calories, and several continue to do so. A third reason is that they're eaten in an unrefined, fresh state.

Potatoes contain an adequate amount of many essential minerals, and due to their low phytic acid content (1), the minerals they contain are well absorbed. They're rich in magnesium and copper, two minerals that are important for insulin sensitivity and cardiovascular health (2, 3). They're also high in potassium, which helps control blood pressure, and vitamin C. Overall, they have a micronutrient content that compares favorably with other starchy root vegetables such as taro and cassava (4, 5, 6), and they offer considerably more micronutrients than refined carbohydrates such as white flour, white rice and white sugar.

On the other hand, I don't have to eat potatoes exclusively, so what do they have to offer a mixed diet? They have a high glycemic index, which means they raise blood sugar more than an equivalent serving of most carbohydrate foods, although I'm not convinced that's a problem in people with good blood sugar control (7, 8). They contain adequate fiber, but less than some other sources of starch. For example, sweet potatoes, an unrelated species, contain more micronutrients and fiber, and have been a central food source for healthy cultures (9). However, the main reasons temperate-climate cultures throughout the world eat potatoes is they yield well, they're easily digested, they fill you up and they taste good.

In the next post, I'll delve into the biology and toxicology of potato glycoalkaloids, and review some animal data. In further posts, I'll address the most important question of all: what happens when a person eats mostly potatoes... for months, years, and generations?


* In terms of calories produced per acre.

** A simplified description. The process can actually be rather involved, with several different drying, stomping and leaching steps.

57 comments:

Jeremy said...

It would be great if you specifically evaluate Loren Cordain's contention that members of the nightshade family lead to leaky guts and other associated diseases.

You can purchase his article "Consumption of Nightshade Plants, Human Health and Autoimmune Disease Implications" (it was free in his newsletter) for $20 at

http://www.thepaleodiet.com/store.shtml

Caleb Cooper said...

I'll be very interested to see part II as potatoes are one of my top choices as a carb source, and I have one almost daily.

I do muscle test with the spine/gut before buying or eating the potatoes though, and assume often when the gut/spine moves away it's because my body isn't done detoxing the glycoalkaloid.

I wouldn't be surprised if people who had potatoes more frequently accumulate enough glycoalkaloid for it to manifest as adverse health effects.

Michael Barker said...

What I think you should address about the potato is its present state and how it compares with a potato, say two hundred years ago.

I truly believe many foods were great years ago but I believe that industrial agriculture has changed much of that.

Ferdinand_K said...

Yeah!
Finally something different and interesting at the food-front again, aside of the paleo blogs and their exhausting mantra "wheat is evil, wheat is evil, carbs are evil, carbs are evil..."

great!

jo said...

And high in potassium. One of my favorite quick to fix meals is a nuked potato with full-fat cottage cheese and salsa.

futrzak said...

What I think you should address about the potato is its present state and how it compares with a potato, say two hundred years ago.

Good point. I am not a chemist, I cannot analyze it myself, but I noticed that potatoes grown on small traditional farms in eastern Europe have different taste, texture and properties when compared to industrially grown potatoes in USA.

EL 66K said...

Stephan, it's a bit off topic, but... do you think nixtamalized corn tortillas (arepas) are fine as a staple? I normally eat them for breakfast.

Paleo Phil said...

If tubers like potatoes and African yams are relatively healthy for humans, then that seems to suggest that we are at least somewhat adapted to eating tubers and perhaps some other starchy foods. Were there any foods prior to the advent of cooking that would have contributed to this adaptation? For example, were African yams eaten raw (with the assistance of drying and/or soaking, perhaps) for a long period before they were cooked, or do you think that humans have had enough time to adapt to tubers since cooking, or are there any other hypotheses?

Valtsu said...

Jeremy: I think Stephan once commented that Cordain's paper in his Whole Health Source article "Sweet Potatoes".

Thanks for the text. I think the second part will be nice reading too. Could you also provide similar text about carrots some day? :P

Valtsu said...

Let me correct my comments... Stephan mentioned Cordain's paper in the _comment section_ of article Sweet Potatoes.

Fredrik Gyllensten said...

Very interesting, potatoes are definitely an important food.

Stephen said...

Yeah Potatoes!

I love yellow and purple potatoes sprinkled with thyme then roasted with goose fat. A good rib eye steak and a hearty Rhone to wash it all down.

Yum.

Justin said...

The article mentioned that potatoes are:

"the most productive crop in the world. (In terms of calories produced per acre.)"

That is an amazing statistic. Is this still the case in today's world of 200-bushel-per-acre corn harvests ?

For those of us who would like to learn more, is there any further reading or reference on this topic ?


thank you

Anand Srivastava said...

@Paleo Phil
Potatoes must have been eaten ever since we learnt to cook. As it is very easy to cook them in a bed of embers.

There is evidence that humans had sophisticated methods (under ground cooking)of cooking by 400,000years ago.
It is possible that humans had control of fire for a million years ago. That is enough time to get adapted to tubers.

Also the fact that we have many more AMY1 genes compared to Chimps, also points in that direction. We were getting a starch source that was much more concentrated than what the chimps could obtain. Such a source must be eaten after cooking, otherwise chimps would get it too. What food fits the bill, except most tubers, some nuts and some fruits. And they are all functionally equivalent. My money is on tubers more than fruits or nuts.

chris said...

Wondering why you didn't mention potassium?

This is my number one reason for eating potatoes.
There are no potassium supplements on the market (> 100mg) and most other forms of potassium rich food are either grain or very high in sugar.

Stephan said...

Hi Jeremy,

I read Cordain's newsletter. I won't be referring to it much (maybe once). However, I do think he overstated the evidence of the potential harmfulness of potatoes.

Hi EL66K,

I think nixtamalized corn is better than corn that has not been nixtamalized, however I don't consider it a very good staple food. The process removes part of the bran, but is not that efficient at reducing phytic acid. One tortilla a day is not a big deal though.

Hi Paleo Phil,

I would say the evidence is rather strong that we're adapted to eating starch. However, that adaptation probably occurred after the control of fire, as raw root vegetables are generally toxic.

Hi Justin,

I'm not 100% sure that potatoes are still more productive than 21st century industrial corn.

Hi Chris,

Just added it.

Martin Levac said...

"Good blood sugar control" is relative. It depends on the amount of insulin required to maintain normal BG. And that depends on the amount of carbs in the diet. The more carbs, the more insulin.

Because some systems take time to gear up, the more carbs you eat chronically, the better the immediate response in a GTT. Conversely, the less carbs you eat chronically, the worse the immediate response to eating a potato, for example.

Chronic hyperinsulinemia is a feature of metabolic syndrome. I don't think I want this just to look good on a GTT.

So is it really "good blood sugar control"?

I prefer to have the worse immediate response if it means I'll have much lower baseline insulin and BG.

Aaron said...

To answer Justin's questions about potatoes vs. corn:

First of all, 200 bushel/acre corn isn't really that common, though you wouldn't know it hanging out at the local feed store. :-) The USDA says the national average is around 160 bushels/acre. At 56 pounds/bushel, that's 8960 pounds/acre.

Potatoes, on the other hand, yield about 40,000 pounds/acre! Those are USDA numbers, so they include commercial growers, but I found figures that said even organic potatoes produce over 20,000 pounds/acre. So there's still a huge difference.

On top of that, potatoes have a shorter growing season (you can plant them twice a year around here, doubling your per-acre production) and aren't usually affected much by pests or weather. It's good to hill them, but corn requires cultivation (or herbicide), so that's a wash. Potatoes only have to be dug and cleaned/peeled, and they're ready to use; corn has to be shelled, cleaned, and then ground or processed in some way.

Potatoes win in pretty much every way except one: they can be bruised by rough handling, so they require a certain amount of hands-on work. Corn, on the other hand, can be almost entirely grown and harvested from the seat of a tractor.

Stephan said...

Hi Martin,

High carbohydrate consumption per se does not lead to fasting hyperinsulinemia. That is a myth that is often repeated but I've never seen it supported by evidence.

Hi Aaron,

Thanks for the analysis. Potatoes are mostly water, but it sounds like they still produce more calories per acre than corn. I would add that another downside to potatoes is that the seed is more expensive. Good quality disease-free seed potatoes are super expensive, at least for the small-scale gardener.

Aaron said...

For what it's worth, the USDA nutrition database says potatoes have 359 calories/pound, dried corn has 1902, and whole-grain cornmeal has 1600. So yeah, corn does even things up quite a bit per acre when you look at calories instead of pounds.

That's true that seed potatoes cost more per plant than most seeds; and instead of multiplying hundreds-fold like corn does, you're doing good to get a couple dozen new potatoes from each seed potato you start with. On the other hand, if you store potatoes over the winter from your late planting, you can use them for seed the next year.

BizJ said...

I love potatoes. They're my starchy carb of choice, for reasons already mentioned: Potassium, and the fact that they're a whole food that you eat in a relatively unprocessed state.

And they're a great vehicle for butter.

Gabriella Kadar said...

Potatoes are the food of revolution. First, because they produce more calories per acre than any other crop they provided peasants with the energy they needed. Second, they can be left buried in the ground so that invading armies had no idea how much food was actually available. Peasants therefore maintained their undiscovered source of nourishment.

Other food crops cannot be hidden like potates.

....just another slant on the value of the potato....

Martin Levac said...

Stephan, when you say "it's a myth that a high carb diet causes hyperinsulinemia", do you mean to say that it's a low carb diet that causes hyperinsulinemia? I mean, if this idea is not true, then the opposite must be true.

If it's not the carbs, then what?

Stephan said...

Hi Martin,

I think macronutrients are not the key to the puzzle. Biological systems are much too complex for the answer to simply be "fat" or "carbs". I believe the key lies mostly in food quality, i.e. refined vs unrefined; industrially vs. traditionally processed.

These factors affect micronutrient density, the quantity and quality of fiber, and the quantity and quality of many other bioactive substances. In addition, there are toxins worth avoiding like wheat gluten and excess sugar.

Marco Turu said...
This comment has been removed by the author.
jaime said...

During the II world War my father & his family were raised basically on sweet potato and potatoes. He always comment that without them they could not have survived. They were healthy until they move to another country and start eating white flour & industrialized crap. They all developed diabetes.

guyberliner said...

Aaron:
Some more counts against corn plantings: they take up a huge surface area, shade out everything else around them, and are really hard on the soil, rapidly depleting it of nutrients in the absence of careful rotation. Whereas potatoes can be planted and grown effectively in nothing more than burlap sacks and barrels! Making them an extremely effective food crop on a small scale and where space is scarce.

Corn practically has to be grown on a massive industrial scale to yield anything substantial -- or else requires back-breaking labor from poor peasants. Think of the terracing of steep slopes a la Mayan peasants -- but actually, if you go to places like Chiapas, you notice that a lot of them are not terraced, out of poverty and desperation, for lack of sufficient time and labor. Instead, the hastily cleared and prepared, formerly forested hillsides where peasant corn "milpas" are planted regularly wash away when heavy rains come. Much of the world's forests, riparian lands, and wildlife habitat are being lost due to the devastation wrought by planting corn on such marginal clearings.

Anand Srivastava said...

@Martin

Just to add more information to what Stephan said.

Read HyperLipid. There are several rat studies showing fat(even good coconut oil) causes obesity, more readily than carbs. But the constant factor in those studies is the lack of nutrients.

It would follow that lack of nutrients causes obesity. They also sometimes use higher fructose to cause the obesity rapidly.

For some reason carbs seem to be better when there is a dearth of nutrients. So actually carbs in itself are not causing trouble. Its actually the lack of nutrients and excess of poisons.

Anand Srivastava said...

Another benefit of Potato plants over corn is that you could allow cattle to graze on them without destroying the crop, as long as the grazing is sparse. It will even be healthy for them. So you get a good yield on your plot and you can get good meat grown as well.

Stephan said...

Hi Anand,

There's a farm here in Washington (Olson) that rotates cows and potatoes on the same fields. The cows and grass fertilize the soil for a few years, then they plant potatoes for a year or two in the fertile soil. It requires no fertilizer, herbicide or pesticide inputs. Seems like a pretty good system.

BizJ said...

Hey Stephan, I just recently moved to Seattle and I was wondering, if you purchase milk, what milk do you buy around here? I've discovered milk from Twin Brook Creamery that is delicious and surprisingly cheap compared to other comparable milks.

It is produced in Lynden, WA from pastured cows, which are also 100% pure, registered Jersey cows. Their milk is richer and also I believe it contains predominantly the A2 type of casein which I've heard has health benefits compared to the A1 type.

I'm not sure where in the Seattle area you live, but their milk is carried at various markets around town.

So, what milk do you buy?

Martin Levac said...

Refining merely allows us to get to the nutrients that are otherwise locked inside the fiber, fiber which is indigestible to humans. In practical terms, we've taken an item that was not food for humans and turned into into an edible substance, we've also made more of it available for absorption. You've written about traditional processing methods for grains so you know exactly what I mean here.

But now if you blame the processing itself, this means that we're killing ourselves with the very thing that is supposed to maintain us alive. That makes no sense.

Don't blame the processing when it's the substance itself that kills us. If it kills us when it's refined, it's not because it's refined, it's because the substance itself is harmful and the refining merely allows more of it to enter our body and do its damage. Refined arsenic is still arsenic.

Some examples where refining does not turn a good substance into a toxic one. Lard, suet, tallow, pemmican. Some examples where refining turns a bad substance into a very bad one. Sucrose, flour, HFCS, agave syrup, margarine.

KOKO said...

Hi Stephan,
Long time no talk! Hope things are well.

I love potatoes, especially mashed and fried. I am curious though, like a previous poster, how our potatoes today, especially the likes of the New Leaf Monsanto monstrosities famously described by Michael Pollan, compare with the potatoes of yesteryear. Am still getting the benefits?
thanks dude!
koji

Walter said...

Everything is dosage dependent. I was lucky when I took my Intro to Biology class, it was taught by a Ph.D. Biochemist. I discussed this with him. The human body actually needs very, very, very, very small amounts of arsenic.

The idea that we get from the holistic health movement, that it got from, oh, I don't know, natural hygiene, that things are toxic regardless of dosage is wrong.

Dr. Eades points out on one of his posts about fructose being harmful, that small amounts of fructose actually improve glucose metabolism.

Stephan said...

Hi Martin,

What substance are you referring to, carbohydrate? There are countless cultures around the globe that eat 70 plus percent carbohydrate and don't suffer from metabolic disorders, so I find that hypothesis hard to swallow. For example, the Papuan highland culture I blogged about recently that eats 90% sweet potatoes, and has virtually no obesity, diabetes or CHD. And the Kitavans, which you may recall me writing a series about last year.

Martin Levac said...

The Kitavans, like all the other isolated populations that were observed by Price, don't eat any refined food. But they are not immune. Once they travel out of their island and adopt a modern diet, they promptly develop the same diseases of civilization as the rest of us. Is it because they now eat their food refined? No, there's something else going on.

Like Stefansson observed, we don't need to adopt a completely different diet to suffer the same disease, we merely have to add refined sugar and flour to our existing diet as he described of those plains Indians who did just that.

So why do the Kitavans continue to enjoy good health in spite of an alleged high carb diet? Because it is not in fact a high carb diet. It's a low carb diet in disguise. How's that? We can't digest fiber. The Kitavans are no different in this respect. But once you transform the fiberous carbs into something where the digestible carbs become suddenly available, the Kitavans lose their alleged high carb immunity.

But maybe you believe fiber is food. Well then there's the rub. If we can't digest it, is it food?

Jack C said...

My wife and I both love potatoes, usually mashed with lots of butter, but a lot of flatulence always follows.

Are there other potato lovers who have experienced this problem?

Stephan said...

Hi Martin,

The Kitavan diet is very high in starch, and only moderately high in fiber. It is not a low-carb diet by any stretch of the imagination. Kitavans eat taro, breadfruit, yams, and sweet potatoes. Those have all been well characterized and they are starchy tubers roughly comparable to potatoes. They have a high glycemic index and glycemic load, like all starchy tubers. The bottom line is that the Kitavans, along with many other cultures, eat lots of unrefined digestible carbohydrate and are healthy.

Colldén said...

Stephan, what is your stance on fruits and fresh 100% fruit juices? It would seem to me that for instance orange juice is comparable to potatoes both in nutrient density and nutrient absorption.

Matt Barber said...

Love your blog Stephan. I think anthropological health studies are fascinating, but I'm only learning enough to be dangerous.

I was poking around for information on the Papuan highland culture, and came across data from the International Association for the Study of Obesity. This data indicates that Papua New Guinea has the highest obesity rate per capita in the world. How ironic that the highland Papuans have "virtually no obesity". That's messed up!

Anand Srivastava said...

@collden

I know you asked Stephan. But my 2 cents anyway.

I think the problem boils down to how fast the fructose in the fruits hit the liver or other tissues in the body. Fructose is toxic except in very small quantities.

When we eat fruits or fructose with other fibrous or fatty foods, the stomach does the portion control. The fructose exits the stomach slowly. So that the rest of the body and the liver gets it slowly, and they can then process it.

When we drink fruit juice or other liquid sources of fructose, then the stomach does not control its passage. It has never been used to any other liquid other than water. It does not try to release it slowly. The effect is that the liver and the rest of the body gets the fructose at a very high rate. Possibly more than it can handle.

In my opinion fructose in liquids should be avoided. I am not sure this does not apply to glucose in liquid as well.

"Guppy" Honaker said...

This is a great post about potatoes. They are so healthy for you (as long as you don't load on the sour creme)! We grow our own here, and they are great with our home-grown organic eggs and spinach!

- David

Aloe Vera 101
Holistic Health Info.

daphne sy said...

Thanks for sharing this post. Today one cannot even imagine vegetables without potatoes. This shapeless and ugly looking tuber, bearing the scientific name Solanum Tuberosum, has cast a spell on us. Potato lovers (including me), and those who do not like them, will be equally delighted to know that potatoes have more in store for them than just carbohydrates and calories.

Kimi Harris said...

I appreciate this post! I've recently added potatoes more into our diets and have liked the fact that I don't have to spend days soaking them, and that they are delicious! Looking forward to seeing the rest of the series.

Kimi @ thenourishinggourmet.com

Francesco said...

@Jack C
Of course Jack. Me too.
I cannot eat even small quantities of potatoes without having so much gas and flatulence after some hours.


Re other cultures eating starches (70% of their total daily calories), could a different level of physical activity be involved, like Dr. Art Ayers says here? http://coolinginflammation.blogspot.com/2009/02/medical-advice-is-just-wrong.html (read "Starch is the problem"...).

I'm not so sure putting a sedentary western man on a 70% carbs/starch diet (even from potatoes) would be a great thing, but that's just my opinion.

Marco

rick said...
This comment has been removed by the author.
rick said...

I would like to know if sweet potatoes and yams contain more glykoalkaloids than white potato. This video I saw by Dr.G... saying white potatoes are to be avoided for glykoalkaloids but says nothing about sweet potatoes and glycoalkaloids (saying they are healthy based on some healthy food guide):

http://www.youtube.com/watch?v=uP9zeW1l7cA&p=53AA35449C7DD652&index=39&hd=1#t=1m Healthy alternative?

Hans Keer said...

I think it is not solely the potato or another nightshade that causes havoc. It's today's combination of grains, legumes, dairy and nightshades that together cause the leaky gut and the complications that arise from that. We wrote posts on the subject.

Stephan said...

Hi Jack C and Francesco,

If potatoes give you GI trouble, then by all means avoid them. There's nothing in potatoes that should give you gas, so it may indicate a sensitivity.

Exercise certainly plays a role in the health of most non-industrial cultures, whether the diet is high in carbs or fat. But keep in mind that many non-industrial agriculturalists don't get much more exercise than walking around, food prep and other domestic tasks. They aren't running wind sprints every morning.

Hi Collden,

I think fruit juice is best avoided except occasinally. Sweet beverages aren't a good idea in general. I'm OK with fruit, within reason. I personally eat 1-2 pieces per day.

Hi Matt,

I'm not surprised. Cultures transitioning to an industrial lifestyle often develop the diseases of civilization to an exaggerated degree.

Hi Rick,

White potatoes and sweet potatoes are botanically unrelated. Sweet potatoes don't contain solanine or chaconine, the two main toxic glycoalkaloids found in white potatoes.

Bravo said...

'll be very interested to see the second part such as potatoes are one of my top choices as a source of carbohydrates, and have one almost every day.

I do muscle testing with the spine guts before buying or eating potatoes though, often assume that when the spine moves bowel away is that my body detoxing non glycoalkaloid.

I would not be surprised if people were more often glycoalkaloid potato accumulate enough to realize it as adverse health effects.

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JohnN said...

@ Martin Levac:
"But maybe you believe fiber is food. Well then there's the rub. If we can't digest it, is it food?"

Perhaps in support of your argument is the actual consideration of fiber as food. First for the population of microbes in your guts that in turn creating the fatty acid absorbed by the human body.
In some cultures this energy source of fatty acid can approach 15% of total - 100% for the ruminants and the mountain gorilla - our closed cousin.
IMO, any hypothesis on human health, diet and/or disease is seriously deficient without taking into account the symbiotic relationship between the body and its microbes.
I suspect it (fiber) can also resolve the paradox of vegetarianism as a health booster.
John

pjnoir said...

I agree with Michael Barker. Agriculture has morphed so quickly that nothing is wehat it was even 50 yrs ago.

I'm reading a wonderful book on Irish cooking- a cookbook with a LOT of history. What the Irish was left to eat is truely amazing, nothing short of rock soup with potatoes and cow blood ( instead of stealing a cow, they let out blood to use as protein) sorry for the off topic.

JBG said...

Caleb Cooper and/or Bravo: What is this spine/gut test you are talking about?

Anna said...

pjnoir

What's the name of the book? Sounds fascinating. I love reading what people *used* to eat.

Caleb Cooper said...

@JBG: you can email me at zetjintsu@y*hoo and I'll explain more so we don't clutter up Stephan's thread.

Stephan, any chance we could see a table listing glycoalkaloid content of different varieties? I got white potatoes last time shopping, and have been annoyed that the spine/gut muscle test is hardly letting me eat any. Coming back to this thread though it sounds like they're the worst variety for toxins.

So what's the lowest glycoalkaloid potato? I'm wondering what's up with those weird purple potatoes I get at the farmer's market as well.

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